Preparation of hydroxyl terminated polymers

ABSTRACT

HYDROXYL TERMINATED POLYMERS, USEFUL AS ADHESIVES AND CAULKING MATERIALS ARE PREPARED BY THE REACTION OF CARBOXYL TERMINATED POLYMERS WITH ETHYLENE OXIDE IN THE PRESENCE OF A TERTIARY AMINE CATALYST.

United States Patent O 3,712,916 PREPARATION OF HYDROXYL TERMINATEDPOLYMERS Alan R. Siebert, Maple Heights, Ohio, assignor to The B. F.Goodrich Company, New York, NY.

N Drawing. Original application May 22, 1968, Ser. No. 731,281, nowPatent No. 3,551,471. Divided and this application July 2, 1970, Ser.No. 52,125

Int. Cl. C07c 69/66 US. Cl. 260-484 R 3 Claims ABSTRACT OF THEDISCLOSURE Hydroxyl terminated polymers, useful as adhesives andcaulking materials are prepared by the reaction of carboxyl terminatedpolymers with ethylene oxide in the presence of a tertiary aminecatalyst.

CROSS REFERENCE TO RELATED APPLICATION This application is a division ofcopending application Ser. No. 731,281, now U.S. 'Pat. 3,551,471, filedMay 22, 1968 by A. R. Siebert.

BACKGROUND OF THE INVENTION .Hydroxyl terminated liquid olefinicpolymers are useful as crosslinking agents with difunctional polymers,as adhesives, and as caulking and potting compounds. They cure readilythrough reaction of the terminal hydroxyl groups with organicdiisocyanates to form solid high molecular weight materials of lowfusibility.

\These liquid polymers may be hydroxyl terminated homopolymers such aspolybutadiene and highly saturated polymers such as polyalkyl acrcylateswhose alkyl moieties consist of 1-8 carbon atoms.

Hydroxyl functional polymers can presently be produced from olefinicpolymers by first converting a portion of the olefinic bonds of thepolymer to ozonide linkages, and then reductively cleaving the ozonidelinkages to produce hydroxy terminated polymer.

Alternative processes of manufacture are desirable and constantly beingsought in the art. Furthermore, polymers prepared by cleavage of highermolecular weight chains as described above generally do not achievehydroxyl functionality at each end of the polymer chains, that is, thefinal hydroxyl functionality is generally con siderably less than 2,often 1.6 to 1.8. For most efficient use of the reactants and theobtainment of best overall properties it is desirable to have finalhydroxyl functionality as close to 2.0 as possible.

SUMMARY OF THE INVENTION Carboxyl terminated polymers of polybutadieneand polyalkyl acrylates are known in the art. It has now been discoveredthat it is possible to convert these carboxyl terminated liquid polymersto hydroxyl terminated liquid polymers wtih a high degree ofdifunctionality, i.e. practically 2, indicative of the fact that anhydroxyl group is located at each end of the polymer chain. The propertyof difunctionality is essential if higher polymers are to be produced bythe subsequent curing reactions. This conversion is accomplished byreaction of liquid carboxyl terminated polymer with 3 to parts perhundred of polymer of ethylene oxide in the presence of 0.1 to 0.3

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part of tertiary amine catalyst. The reaction medium may be any solventthat will dissolve the carboxyl terminated polymers, and the hydroxylterminated polymer which is formed. Acetone, tertiary butanol, methylethyl ketone, cyclohexanone, cyclohexanol, tetrahydrofuran and dioxaneare typical solvents that may be used.

Optionally the addition reaction may be run in a mass or bulk systemwith no solvent medium being employed. In such cases the ethylene oxideis preferably employed in excess to insure [fluidity and accomplishsatisfactory heat transfer.

'Carboxyl terminated polymers of butadiene and polyalkyl acrylate can beproduced by the process taught in United States Pat. 3,285,949.Preferably the desired monomers are placed in a solvent with a low chaintransfer potential, preferably tertiary butanol, and a bis-azocyano acidinitiator, preferably azodicyanovaleric acid is added. Polymerizationsare run at -80 C. Product polymer is thrown down with methanol andseparated by decantation. These carboxyl terminated polymers are curablewith diisocyanates. It has been discovered that when the liquid carboxylterminated polymers are reacted with ethylene oxide, the chain terminalgroups are opened up and converted from carboxyl to hydroxyl.

Carboxyl terminated polymers are used as adhesives and caulkingcompounds, but they do not cure completely satisfactorily with epoxyresins. Trifunctional aziridinyl compounds are currently used to cureproducts using carboxyl terminated adhesives or hinders. These systemsunfortunately have low elongations and they age poorly. A more desirablecuring reaction is that between a terminal hydroxyl group and adiisocyanate. No undesirable products are formed and high adhesivestrengths are attained. Catalysts that may be employed for theconversion of carboxyl terminated polymer to hydroxyl terminated polymerinclude primary, secondary and tertiary, mono and polyamines.Particularly preferred are trimethyl amine, triethyl amine, tributylamine, triisoamyl amine and the like. Catalyst is employed in the rangeof 0.1 to 0.3 part per hundred parts of liquid carboxyl terminatedpolymer.

Molecular weights of the polymers are determined with a Mechrolab VaporPressure Osmometer using methyl ethyl ketone (MEK) or toluene as thesolvent. The instrument is calibrated with azobenzene and sucroseoctaacetate. Molecular weight may also be calculated from the chemicalequivalents per hundred of rubber of carboxyl (ephrz) value determinedby titration of polymer solution with alcoholic KOH to a phenolphthaleinendpoint. Functionality of the polymer is defined as the ratio of theosmometer molecular weight (corrected for antioxidant, if any ispresent) to the calculated ephr. molecular weight times 2, the idealnumber of functional groups per molecule.

Brookfield viscosity, employing an LVT model viscometer and a #4 spindleis run on the freshly prepared polymers. Values up to 50, 00080,000 cps.are accepted by the art as indicative of pourable, easily handledmaterials.

DETAILED DESCRIPTION OF THE INVENTION Example 1 A bottle polymerizationof butadiene in tertiary butanol is conducted using azodicyanovalericacid catalyst. When the catalyst is about decomposed, the excessbutadiene is vented and the bottle contents are added to methanol withstirring to throw down the liquid polymer. After settling, themethanol-teritary butanol layer is decanted. One partphenylbetanaphthylamine antioxidant is added to the polymer per 100parts of polymer which is then dried in a Rinco evaporator to constantweight.

TABLE 1 Tertiary butanol "parts-.. 100 Butadiene do 100Azodicyanovaleric acid do 4 Temperature C 70 Polymerization time .hrs 16Polymer yield g 16.5 COOH/ephr. (equivalent per hundred parts rubber).0515 Brookfield viscosity at 27 C. cps 49,000 iTm-MEK 3840 Kin-calc.1.98 Functionality 1.98

100 parts of the carboxyl terminated polymer are added with 1 partsacetone to a quart glass polymerization bottle. The bottle is flushedwith nitrogen, capped with a puncture sealing cap and placed in a 90-95C. bath until polymer is completely dissolved. After the polymersolution is cooled to about 25 C., varying parts of ethylene oxide andtrimethyl amine are injected through the sealing cap. The esterificationis conducted to completion in the 90-95 C. bath. Reaction is followed bytitrating an aliquotfrom the bottle with standard base usingphenolphthalein indicator. The hydroxyl terminated polymer is recoveredby drying the solution on a Rinco evaporator to remove acetone andexcess ethylene oxide and drying for 30 minutes at 90 C. with a pressurebelow 2 mm.

The following data is observed on the hydroxyl terminated polybutadiene:

The procedure of Example 1 is repeated with difierent tertiary aminecatalysts and occasionally with an antioxidant,2,2'-methylenebis(4-methyl-6-t-butylphenol) added to the carboxylterminated polymer.

100 in. parts of hydroxyl terminated polymer are mixed in an aluminumpan with 4 m. parts toluene diisocyanate at a ratio of one equivalent ofhydroxyl to one equivalent of isocyanate curing agent. Pot life ismeasured by lifting the mixture on a spatula at intervals. When it hasbecome too viscous to spread, the pot life time is recorded.

TABLE 3 C D E F G Carboxyl terminated polybutadiene 100 100 100 100 100Antioxidant at 1.25 phr No No Yes Yes Yes Acetone 100 100 100 100 100Trimethylamine 11 08 1 1 Triisoamylamine. 38 Ethylene oxide 4 4 4 4 4Pot life with 1.0 equivalent of toluene diisocyanate i- 30 l 60 1 l0 1 21 2 1 Minutes. 2 Hours.

A pot life of greater than 2 hours is desirable for most applications ofadhesives. For occasions where faster pot life, say 6: hour up to twohours, is desired, these materials meet the qualification.

EXAMPLE 3 A carboxyl terminated polybutyl acrylate is prepared inacetone by adding monomers and solvent to an evacuated and nitrogenpurged polymerization vessel under nitrogen pressure. Polymerizationruns 4 hours at C. and the product polymer is thrown down with methanoland recovered by decantation.

TABLE 4 Material: Parts N-butyl acrylate 97 Butadiene 3 Acrylic acid 0.4Azodicyanovaleric acid l2 COOH/ephr. .102 Brookfield viscosity at 27 C.cps. 70,000

The liquid carboxyl terminated polybutyl acrylate is reacted withethylene oxide in presence of triisoamyl amine by the process set forthin Example 1 to produce hydroxyl terminated polybutyl acrylate.

TABLE 5 Carboxyl terminated polybutyl acrylate 100 Ethylene oxide 5Triisooamylamine g .8 COOH/ephr. .003 Brookfield viscosity at 27 C. cps.41,500 Pot life with 1.0 equivalent of toluene diisocyanate "hrs-.. 2

When fully cured, usually in less than 24 hours, the products of thisinvention are dry to the touch and elastomeric in nature. They can bedented by pressure, as by a finger nail, but will resume their shapewhen the pressure is released.

What is claimed is:

1. Liquid hydroxyl terminated polymers selected from the classconsisting of polybutadiene and polyalkyl acrylates whose alkyl moietyconsists of l8 carbon atoms said polymers being prepared by the reactionof liquid carboxyl terminated polymers selected from the classconsisting of carboxyl terminated polybutadiene and carboxyl polyalkylacrylates whose alkyl moiety consists of 1-8 carbon atoms, said carboxylterminated polymers being prepared by the reaction of butadiene andmonomeric alkyl acrylates in tertiary butanol at 7080 C. in the presenceof a bis-azocyano acid with 3-10 parts per 100 parts of liquid carboxylterminated polymer of ethylene oxide in the presence of 0.1 to 0.3 partper hundred parts of liquid carboxyl terminated polymer of an aminecatalyst selected from the group consisting of trimethyl amine, triethylamine, tributyl amine and triisoamyl amine in a reaction medium selectedfrom the group consisting of acetone, tertiary butanol, methyl ethylketone, cyclohexanol, tetrahydrofuran and dioxane, said reaction mediumbeing maintained at about 90 -95 C.

2. The liquid hydroxyl terminated polymers of claim 1 Where the liquidcarboxyl terminated polymer is polybutadiene.

3. The liquid hydroxyl terminated polymers of claim 1 where the liquidcarboxyl terminated polymers is polybutyl acrylate.

References Cited UNITED STATES PATENTS 3,360,545 12/1967 Wygant 260-485HENRY R. JILES, Primary Examiner P. I. KILLOS, Assistant Examiner US.Cl. X.'R. 260-486 R V UNI'IED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3, 7 2, 9 Dated January 23, 1973 Inventor(g) AlanR.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

= Column 1, line 35, change "acrcylat es" to read ---acrylates---; 5column 1, line "8, change "'wtih to read ---.with--; column 3, line 2,change "teritary" to read --certiary--; column 3, l line 18 of Table l,h "1.98" should read 880---5 column 3, line tg of Table 2, under sectionB, "1.95 should read Signed and sealed this 13th dayof Novembef 1973.

(SEAL) Attest: EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting OfficerActing Commlssloner of Patents UscoMM-Dc some-P09 a [1.5 GOVERNMENTPRINTING OFFICE I 969 Q'-3 6$-QI4

